On Wed, May 12, 2021 at 04:43:33PM +0200, Christophe Leroy wrote: > Le 12/05/2021 à 16:31, Segher Boessenkool a écrit : > >On Wed, May 12, 2021 at 02:56:56PM +0200, Christophe Leroy wrote: > >>Le 11/05/2021 à 12:51, Segher Boessenkool a écrit : > >>>Something seems to have decided this asm is more expensive than it is. > >>>That isn't always avoidable -- the compiler cannot look inside asms -- > >>>but it seems it could be improved here. > >>> > >>>Do you have (or can make) a self-contained testcase? > >> > >>I have not tried, and I fear it might be difficult, because on a kernel > >>build with dozens of calls to csum_add(), only ip6_tunnel.o exhibits such > >>an issue. > > > >Yeah. Sometimes you can force some of the decisions, but that usually > >requires knowing too many GCC internals :-/ > > > >>>>And there is even one completely unused instance of csum_add(). > >>> > >>>That is strange, that should never happen. > >> > >>It seems that several .o include unused versions of csum_add. After the > >>final link, one remains (in addition to the used one) in vmlinux. > > > >But it is a static function, so it should not end up in any object file > >where it isn't used. > > Well .... did I dream ? > > Now I only find one extra .o with unused csum_add() : That's > net/ipv6/exthdrs.o > It matches the one found in vmlinux. > > Are you interested in -fdump-tree-einline-all for that one as well ?
Sure. Hopefully it will show more :-) Segher
